This is another followup of D24562
These tests are of the form
try { action-that-may-throw assert(!exceptional-condition) assert(some-other-facts) } catch (relevant-exception) { assert(exceptional-condition) }
Under libcpp-no-exceptions there is still value in verifying
some-other-facts while avoiding the exceptional case. So for these tests
just conditionally check some-other-facts if exceptional-condition is
false. When exception are supported make sure that a true
exceptional-condition throws an exception